Preparation of dihydrothiazoles

ABSTRACT

This invention relates to dihydrothiazoles and to the preparation thereof by reacting aza-alkylene-dienes with sulfur.

This is a division of application Ser. No. 112,506, filed Jan. 16, 1980now abandoned.

In U.S. Pat. No. 4,106,904 there is described the reaction of aldehydewith ammonia. Where the alpha carbon of the aldehyde is unsubstituted, acyclic compound is formed in accord with the following equation:##STR1##

However, as disclosed by Hasek et al J Org Chem 26, 1822 (1961) wherethe alpha carbon is substituted non-cyclic, compounds are formed inaccord with the following reactions: ##STR2##

I have now discovered that where Compounds I and/or II are reacted withsulfur, dihydrothiazoles are formed.

This is illustrated by the following reaction: ##STR3##

The reaction is carried out by heating a mixture of Compound I or II andelemental sulfur in stoichiometric amounts at temperatures from 40°-160°C. for 1-24 hrs. Solvents which do not interfere with the reaction maybe used but are not necessary.

R and R', which are the moieties of the aldehyde reactant, may be anygroup which does not interfere with the reaction such as alkyl,cycloalkyl, aryl, aralkyl, alkarylalkyl, etc., but preferably alkyl.

Thus, in the dihydrothiazoles of this invention of the formula ##STR4##R" is a branched hydrocarbon, preferably branched alkyl such as ##STR5##where R and R' have the same meaning as the R and R' groups at position5.

The following examples are presented for purposes of illustration andnot of limitation.

EXAMPLE 1 3,7-Diethyl-5-azanona-3,5-diene

To a sample of 250 grams of 28% ammonium hydroxide was added 215 gramsof 2-ethylbutyraldehyde and the heterogeneous mixture was stirred for 18hours at ambient temperature. The resulting organic layer was separated,and after drying, slowly distilled at atmospheric pressure to yield148.8 grams of 3,7-diethyl-5-azanona-3,5-diene.

Mass spectrum m/e=181. ¹³ C nuclear magnetic resonance spectrum, solventCDCl₃, ref. TMS. ##STR6##

EXAMPLE 2 2,5-Dihydro-5,5-diethyl-2-(1-ethylpropyl) thiazole

A sample of 147.8 grams of 3,7-diethyl-5-azanona-3,5-diene, prepared asdescribed in example 1 and 26 grams of elemental sulfur were heated at150° C. for 19 hours. The resulting product was distilled underdiminished pressure and the fraction b.₂₅ 145°-150° C., was identifiedas 128 grams of 2,5-dihydro-5,5-diethyl-2-(1-ethylpropyl) thiazole.

Mass spectrum m/e=213, ¹³ C nuclear magnetic resonance spectrum, solventCDCl₃, ref TMS. ##STR7##

EXAMPLE 3 2,6-Dimethyl-4-azahepta-2,4-diene

To 1400 grams of a 28% solution of ammonium hydroxide was added withstirring over a 4 hour period 1400 grams of isobutyraldehyde while areaction temperature of 22°-47° was maintained. After completion of theaddition stirring was continued for 18 more hours. The resulting organiclayer was refluxed under azeotropical conditions until ammonia evolutionceased (14 hours). The resulting 1137.8 grams of product was identifiedas 2,6-dimethyl-4-azahepta-2,4-diene.

Mass spectrum m/e=125. ¹³ C nuclear magnetic resonance spectrum, solventCDCl₃, reference TMS. ##STR8##

EXAMPLE 4 2,5-Dihydro-5,5-dimethyl-2-(1-methylethyl) thiazole

A mixture of 364.9 grams of 2,6-dimethyl-4-azahepta-2,4-diene preparedas described in example 2 and 93.6 grams of elemental sulfur was heatedfor 6 hours at 145° C. The resulting product was distilled underdiminished pressure and the fraction b.₂₅ 91°-93° C. was identified as280 grams of 2,5-dihydro-5,5-dimethyl-2-(1-methylethyl) thiazole.chemical ionization mass spectroscopy m/e=157, 142, 124, 114, 90, 86. ¹³C nuclear magnetic resonance spectrum. Solvent CDCl₃, Ref. TMS. ##STR9##

Using the procedures of examples 2 and 4, several other substituted2,5-dihydrothiazoles were prepared from the corresponding unsaturatedimines. The results are summarized in Table I.

                  TABLE I                                                         ______________________________________                                        Ex-                                                                           am-                                                                           ple                                                                           No.  Starting imine   Product                                                 ______________________________________                                        5    4,9-Diethyl-7-azatri-                                                                          2,5-Dihydro-5-butyl-5-ethyl-                                 deca-5,7-diene   2(1-ethylpentyl)thiazole                                      ##STR10##                                                                                      ##STR11##                                                6  3,7-Dimethyl-5azanona-                                                                         2,5-Dihydro-5-ethyl-5-methyl                                 3,5-diene        2-(1-methylpropyl)thiazole                                    ##STR12##                                                                                      ##STR13##                                              ______________________________________                                    

The compositions of this invention have a wide variety of uses. Forexample, they are useful as corrosion inhibitors, antioxidants, fuel oiladditives, etc.

I claim:
 1. A process of preparing a dihydrothiazole of the formula##STR14## which comprises reacting a corresponding reactant of theformula ##STR15## where R and R' are selected from the group consistingof alkyl, cycloalkyl, aryl, aralkyl and alkarylalkyl, with sulfur instoichiometric amounts at temperatures of from 40°-160° C. for 1-24hours.
 2. The process of claim 1 where R and R' are alkyl.